Beretta V6-173 2.8L (1989)
Fuels
Oxygenated fuels, with methanol and/or ethanol blended into the gasoline have lower energy and thus reduce fuel economy. Typically there is about a 1
MPG penalty for a vehicle which gets 25 to 30 MPG on 100 percent gasoline.
Using fuels of a lower octane than the vehicle was calibrated to will cause increased "KS" Knock Sensor system activity. This will result in a net
decrease in spark advance and thus poorer fuel economy. Using fuel of a higher octane than the vehicle was calibrated for WILL NOT increase fuel
economy.
Variations in how much fuel is added to the fuel tank during re-fueling can greatly affect calculated fuel economy. These effects decrease as the distance
traveled and the number of tank fillups increase.
Green Engine
New vehicles have not yet had an opportunity for the engine to break in, (rings to seat ... ). A typical engine will take 3 to 5 thousand miles to break in
and during this time period a gradual increase in fuel economy can be expected.
Parasitic Loads
Air conditioning and/or electrical loads, (headlights, heated backglass ... ) also result in lower fuel economy, (typically less than 1 MPG difference, each
10 AMPs takes approximately .4 MPG).
Road Conditions
Road surface condition impacts fuel economy. Gravel and/or pot holed roads decrease fuel economy. Hills (vs. level terrain) also negatively impact fuel
economy. Even gradual unperceptible increases in elevation result in real measurable decreases in fuel economy. Similarly, driving in the rain or snow
decreases fuel economy.
Suspension
Vehicle suspension misalignment can cause poor fuel economy. Check all four tires for abnormal and/or premature tire wear.
New tires, tire rotation, and/or front end alignment may be required to correct fuel economy.
Tires
Performance tires and/or tires with larger "contact areas," (like 60 series aspect ratio), can cause as much as 3 MPG lower fuel economy when compared
to hard "thin" tires. Find out if the tire size currently on the car is the same as original equipment. Replacement tires tailor than original equipment tires
cause the odometer to read LESS THAN actual distance traveled. This will result in lower calculated fuel economy than actual fuel economy.
Tire Pressure
Harder tires, (more air pressure, or different tire compositions) result in better fuel economy. Do not exceed maximum pressure as labeled on the tire,
typically 30-35 psi. The disadvantage of this is that the greater the tire pressure, the harsher the vehicle ride.
Transmission
On 4-Speed automatics, it is possible to drive the vehicle in 3rd gear rather than "overdrive" and not perceive it. Typically this condition occurs when the
shift indicator, or the shift linkage/detent is misadjusted. Misadjusted shift linkage can also result in improper signals to the ECM, which can result in
less spark advance, and results in a drop in fuel economy.
Driving a vehicle in 3rd gear rather than overdrive at highway speeds typically results in a 3 to 5 MPG penalty.
Torque Converter Clutch operation is essential for good fuel economy. A non-locking torque converter typically results in a 1 to 2 MPG penalty at
highway speeds.
Vehicle Weight
Each 125 lbs. of additional weight results in a .3 MPG loss of fuel economy. Thus, additional passengers, luggage ... will decrease fuel economy.
Vehicle Wind Resistance
More wind "DRAG" means less fuel economy. Thus, hang-on luggage carders, cat toppers, open windows and/or open trunk... mean less fuel economy.
(See "Driving Habits").
